Technical Field
The invention relates a loudspeaker system, and more particularly, a loudspeaker system that actively cancels an interaction between loudspeakers sharing the same enclosure.
Description of Related Art
In a loudspeaker system, a plurality of loudspeakers (also referred as drivers or acoustic transducers) may be mounted on the same enclosure box, where the loudspeakers would share the same inner space with in the enclosure box. When sharing the same inner space, the movement of the diaphragm of one loudspeaker would affect the diaphragm of another loudspeaker due to the acoustic pressure change within the enclosure box. This influence would be most notorious in low frequencies, where the loudspeakers have a large diaphragm excursion.
For example, the loudspeaker system may include a first loudspeaker and a second loudspeaker sharing the inner space of the enclosure box. When the first loudspeaker is activated, the movement of the diaphragm corresponding to the first loudspeaker would compress or expand the volume of the air within the inner space of the enclosure box. Assuming that the second loudspeaker is idle (i.e., not active), the diaphragm of the second loudspeaker would be affect by the movement of the diaphragm of the first loudspeaker due to the compression or expansion of the air within the inner space of the enclosure.
When the first and second loudspeakers are in phase, an interaction between the movement of the diaphragms of the first and second loudspeaker would attenuate the peak displacement of the diaphragm of each loudspeaker. On the other hand, when the first and second loudspeakers are out of phase, the interaction between their diaphragms would obtain a greater diaphragm excursion. This situation would generate clipping distortion and may damage the loudspeaker. In addition, if the generated frequency is low and the loudspeakers are close to each other, the acoustic pressure generated is cancelled in the far field (which starts at few centimeters for low frequency.) In this situation, the diaphragm of the loudspeakers would move, however, no sound would be generated, causing a waste of energy.
Conventionally, enclosure box may be designed with compartments, where each of the loudspeakers being mounted on the enclosure box would have its own inner space, so that the interaction between the loudspeakers due to the change of air volume inside of the enclosure box is removed. However, the compartments would decrease the volume where the speakers are mounted, therefore the low frequency performance of the loudspeaker system will be compromised.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.